script, test: add missing python type annotations

Fix warnings for these files when ./test/lint/lint-python.py is run using
mypy 0.991 (released 11/2022) and later:

"By default the bodies of untyped functions are not checked, consider using
--check-untyped-defs [annotation-unchecked]"

For details, see:

https://mypy-lang.blogspot.com/2022/11/mypy-0990-released.html

test/functional/p2p_message_capture.py

@@ -19,7 +19,7 @@ TIME_SIZE = 8
 LENGTH_SIZE = 4
 MSGTYPE_SIZE = 12
 
-def mini_parser(dat_file):
+def mini_parser(dat_file: str) -> None:
     """Parse a data file created by CaptureMessageToFile.
 
     From the data file we'll only check the structure.